1. Field of the Invention
The present invention relates to a developing apparatus to be used in an image forming apparatus such as a copying machine and a laser beam printer using an electrostatic recording process or an electrophotographic process, and configured to develop an electrostatic image formed on an image bearing member with developer including toner and carrier.
2. Description of the Related Art
Hitherto, in image forming apparatus such as a copying machine, an electrostatic latent image formed on a photosensitive drum serving as an image bearing member is developed into a visible image by a developing apparatus.
The developing apparatus is configured to supply toner to the photosensitive drum so as to visualize the latent image as a toner image. A developing apparatus using single-component developer containing magnetic toner as developer has been employed, and a developing apparatus using two-component developer which is a mixture of non-magnetic toner and magnetic carrier has also been employed in many cases. Development of the latent image with the two-component developer is excellent in stability of a toner charge amount, and hence color images can be formed with excellent color tone. For this reason, the two-component developer is suited to use in color-image forming apparatus.
In the developing apparatus, the developer reduced in density as a result of the development may be re-supplied to a developing sleeve without being sufficiently agitated. In this case, troubles such as image density unevenness may occur. Therefore, as a configuration for suppressing the image density unevenness, a developing process of a so-called separate function type has been employed as disclosed in Japanese Patent Application Laid-Open No. 2000-10336 and Japanese Patent Application Laid-Open No. 2012-133212. In the developing process of the separate function type, a developing chamber configured to supply developer to a developing sleeve and a collecting chamber (agitating chamber) configured to collect the developer from the developing sleeve after the development are separately formed so as to perform circulation agitation. With this, the rotation of the developer reduced in density together with the developing sleeve can be suppressed.
Further, the developing apparatus includes a regulating blade configured to regulate an amount of developer to be coated onto the developing sleeve serving as a developer carrying member of the developing apparatus. The developing sleeve is provided so as to face a part of a photosensitive member in a circumferential direction, and is generally arranged side by side with the photosensitive drum due to the restriction on the arrangement of other process units. Thus, the regulating blade is mostly arranged above or below the developing sleeve.
As described above, in the separate function type, when the regulating blade is positioned below the developing sleeve in the gravity direction, the following problem arises.
The developer to be regulated with the regulating blade and accumulated in a developing container is liable to be accumulated in the developing container after falling downward due to the gravity. The accumulated developer becomes immovable while being pressurized by developer conveyed successively to a position facing the regulating blade, resulting in an immobile layer. The developer accumulated into the immobile layer is rubbed by the developer that is being conveyed and moved, thereby raising a problem in that the life of the developer is shortened.